Here's another "my biochem class got me ta thinkin'" post, so if you didn't enjoy the last one, you might want to just hit the backspace button right now.
Actually, it wasn't just my class. I've been watching this show on Cartoon Network, Trinity Blood. It's great. Vampires vs. Christianity, with the Vatican running the western European empire while the Vampires control the eastern empire. In the show, vampires no longer have to feed on humans, which made me wonder what exactly they did to arrange this, which led me to wonder how a vampire might work, biologically speaking.
Of course, not all of the typical "lore" surrounding vampires would probably survive a scientific shakedown, but let's see what we can do.
First, let's consider vampires' incredible speed and strength. All physiological energy comes from the production of ATP in metabolism, due largely to the function of the mitochondria. Tissues which require more energy, and thus work harder, require more ATP and so have more mitochondria. Muscle cells, especially heart muscle, have a lot. So, maybe vampires get their physical prowess from an increased number of mitochondria in each cell.
That seems too easy, though. Just for kicks and grins, let's also hypothesize that they have an increased number of andrenergic receptors (cellular receptors which act as receivers for the signal adrenaline gives).
Okay, so we have a somewhat sensible take on stamina . . . what about their desire to drink blood? Well, mitochondria being as abundant as they are, the vampire's metabolic needs are probably much different. I would imagine they'd need to replace their materials more often. Part of the processes of the mitochondria are dependent on a protein called cytochrome C, which requires a heme group to function. You know what else is abundant in heme? If you said hemoglobin, you win the prize! (A lame blog post! Woo!) I'd guess that the thirst for blood comes from the need for heme. If their mitochondria are working overtime, those coenzymes aren't going to replace themselves.
Hm . . . what about silver toxicity? It's not uncommon for people to have allergies to metals (though I'm unfamiliar with the pathways involved in those). Perhaps it could be a racial allergy? I guess, but I think I actually have an possible explanation.
In the mitochondrial pathways (can you guess what I've been studying lately?), one of the molecules is dependent on copper ions. When studying copper binding proteins, silver can often make a suitable substitute, as the monovalent ions hold similar properties. However, it's not very good for the protein, typically. And I doubt it'd be very good for the vampire if his mitochondrial copper was being replaced with silver.
Not a very thorough explanation, but this isn't exactly going to be submitted to Science or Nature, so I'm not concerned.
The last one I think I can (reasonably) attach a biological function to is the sunlight allergy. Actually, it's not unusual for people to develop allergies to light in certain situations. People undergoing photodynamic therapy often run the risk of acquiring a sunlight allergy. It's because the drugs react with light to cause a reaction which can kill toxic cells, but it's hard to keep the drug in just the harmful cells. So, until the drug is eliminated from the system, most people have to limit sun exposure.
The same could be said for vampires. They're incredibly pale, so their skin cells most likely ceased to produce melanin. Perhaps the enzymes which manufacture melanin mutated so that the product is instead a photodynamic molecule which can cause the same reactions.
Of course, most vampires don't just shrivel up and die in sunlight, but actively burst into flames. I can't really come up with anything for that one. But an overactive photosensitizer instead of melanin seems to be at least somewhat plausible.
Not that plausibility really matters. We're talking about vampires, after all. But this was fun nonetheless.
Better geekery through science.